Ultrasound potentiated salinity effect on growth and metabolite production in Dunaliella salina cells

Manipulating cell cultures by elicitors is one of the important strategies for induction of valuable metabolites in plant biotechnology. Therefore, in this study the effect of ultrasound and salinity on growth, primary and secondary metabolite production was studied in Dunaliella salina microalgae cell culture. Cell cultures were treated with sodium chloride salt at concentrations of 2 and 3 M and ultrasound (40 kHz) for the 2.5, 5 and 10 minutes in a completely randomized design with three replications. The evaluated parameters were cell growth, total protein content, photosynthesis pigments (chlorophyll a and b, total chlorophyll and carotenoids), antioxidant potential, membrane lipid peroxidation, amount of phenolic compounds, flavonoids, anthocyanins, soluble sugars, &beta-carotene and glycerol. The results showed that with increasing duration of exposure to ultrasound and salt concentration the cell growth and photosynthetic pigments were declined. In contrast, total protein, antioxidant potential, membrane lipid peroxidation, the amount of phenolic compounds, flavonoids, anthocyanins, &beta-carotene and glycerol were increased. The highest amount of &beta-carotene was achieved in the case of individual treatment of ultrasound irradiation at 10 min, 3 M salinity and combination of the two factors, with values of 12.3, 11.9 and 14.8 mg/l, respectively. The highest content of glycerol was measured in 3 M salinity, 10 min ultrasound irradiation and combined treatment of the two factors, 11.7, 13.5 and 16.8 mg/l, respectively. It appears that ultrasound potentiated the salinity effect and induced defense responses, secondary metabolism and so increased the amount of cells &beta-carotene and glycerol.